My research led me to Alfred Hicthcock Geek who explains The Kiss by Rodin was a sculpture admired by Hitchcock and how the kissing scenes from Hitchcock's films have been compared to this sculpture.

Hitchcock and Rodin loved the sensuality of the human form – both genders included. They had a healthy sense of the ambivalence of the human condition: that we are no better than animals, yet can approach the nobility of gods; that while happiness can be pursued, it cannot be attained; that when it comes to human passions, comedy and tragedy are one and the same.

Hitchcock's love scenes have often been compared to Rodin's The Kiss. The voyeurism I mentioned above was deliberately implied in many of Hitch's kissing scenes. Speaking of his famous 2 ½- minute kiss in Notorious (1946), he said it was “it was a kind of temporary menage a trois.” Similarly, the erotic power of The Kiss was such that when Rodin loaned it out to the World's Columbian Exposition in Chicago in 1893, it was hidden away in a separate chamber, viewable only upon special application. You'd have thought it was radioactive.

My research also led me to this video essay by Writing with Hitchcock which goes into more details about the Hitchcock kiss.

Discussion of the kissing scenes in Alfred Hitchcock's films—his preference for having the camera circle around the lovers, the influence of Auguste Rodin's sculpture "The Kiss" on his love scenes, and the way in which multiple kissing sequences are used to illustrate the relationship between the principal characters in several of his films, most notably in VERTIGO and NOTORIOUS.

I leave you with these delicious kissing scenes from four different Hitchcock films. Enjoy!